We have localized immunoreactive TGF-beta isoforms in a variety of adult and embryonic tissues using specific peptide antibodies to TGF-Beta proteins and the avidin-biotin peroxidase staining technique. Localization of MRNA for the TGF-Beta isoforms by in situ hybridization is also in progress. In mouse and chick embryos, TGF-Betas have been localized to a number of tissues and were often found at sites of critical mesenchymal-epithelial interactions. Comparison of in situ hybridization and immunohistochemical studies for TGF-Beta3 in chick embryos indicates that in some organ systems such as intestine and cartilage, TGF-Beta synthesized by one cell type may have paracrine actions on neighboring cells. Localization of TGF-Betas 1, 3, and 5 in adult mouse, chicken, and frog, respectively, are remarkably similar and suggest an important role for TGF-Betas in maintenance of heart, kidney, cartilage, and bone. Changes in TGF-Beta expression in a number of pathologic conditions are also being investigated. In human breast tissue, expression of TGF-Betas 1, 2, and 3 is similar in epithelium from normal tissue and carcinomas, while in prostatic epithelium, carcinomas show unique expression of TGF-Beta2 and 3, which are not found in normal tissue. Expression patterns of TGF-Betas 2 and 3, which have been determined for the normal central and peripheral nervous systems, are now being defined for pathologic conditions such as ischemia, Parkinson's disease, and nerve transection. Possible neurotrophic effects of TGF-Betas are being investigated in vitro.